摘要:

AbstractRecent investigations have suggested that the morphological effects of monocular deprivation can be explained by a developmental competitive interaction between the pathways from the two eyes. This study presents evidence in the tree shrew for binocular competition and for an unequal effect of such competition on the different layers of the lateral geniculate nucleus.The effects of monocular deprivation were evaluated by comparing cell size changes in the binocular and monocular segments of the lateral geniculate nucleus in three tree shrews raised with one eye sutured. In two of these animals the open eye was injected with3H proline in order to identify accurately geniculate layers innervated by the non‐deprived eye. Cell sizes in three normal animals and one monocularly enucleated animal were measured for comparison.The results show the following main effects: First, that monocular deprivation significantly changes cell size in the binocular but not the monocular segment of the geniculate nucleus. Comparisons with cell size in normal animals indicates that non‐deprived cells may grow in response to deprivation. Second, that cell size in geniculate lamina 3 is not affected by monocular deprivation, suggesting that cells in this layer are morphologically or functionally secluded from competitive interactions affecting the other layers. Finally, that monocular enucleation in the adult tree shrew affects all parts of the geniculate nucleus including layer 3 and the monocular segment, demonstrating that these parts of the geniculate nucleus are responsive to lack of retinal innervat

ISSN:0092-7317    

DOI:10.1002/cne.901790302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe connections between the nucleus isthmi and the tectum in the frog have been determined by several anatomical techniques: iontophoresis of horseradish peroxidase into the tectum, iontophoresis of3H‐proline into the nucleus isthmi and the tectum, and Fink‐Heimer degeneration staining after lesions of the nucleus isthmi. The results show that the nucleus isthmi projects bilaterally to the tectal lobes. The ipsilateral isthmio‐tectal fibers are distributed in the superficial layers of the tectum, coincident with the retinotectal terminals. The contralateral isthmio‐tectal fibers travel anteriorly adjacent to the lateral optic tract and cross the midline in the supraoptic ventral decussation, where they turn dorsally and caudally; upon reaching the tectum, the fibers end in two discrete layers, layers 8 and A of Potter. The tectum projects to the ipsilateral nucleus isthmi and there is a reciprocal topographic relationship between the two structures. Thus, a retino‐tecto‐isthmio‐tectal route exists which may contribute to the indirect ipsilateral retinotectal projection which is observed electrophysiologically. The connections between the nucleus isthmi and the tectum in the frog are strikingly similar to the connections between the parabigeminal nucleus and the superior collicul

ISSN:0092-7317    

DOI:10.1002/cne.901790303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase was applied to proximal ventral roots of the coccygeal and sacral spinal cord of cats. Subsequent histochemical reaction resulted in extensive staining of spinal cord neurons that had processes in the ventral roots. This procedure was used to study four issues concerning ventral root neurons. (1) Extensive transverse dendritic arborizations were revealed for large and small neurons presumed to be α and γ motoneurons respectively. Dendrites from these neurons were found to project heavily into the ipsilateral white matter, both laterally and ventrally. Dendrites also projected extensively through the anterior commissure, attaining the contralateral grey and white matter. (2) Medially‐located efferent neurons were found to contribute the contralateral dendrites as well as some dorsally‐directed dendrites. Laterally‐located neurons projected dendrites extensively into the lateral and ventral white matter. (3) Stained neurons were found in the intermediolateral cell column, and were presumed to be preganglionic efferent neurons. Some of these neurons projected dendrites into the marginal zone of the dorsal horn, while others sent dendrites medially toward the central canal. (4) Stained fibers, presumed to be primary afferents, were found to enter from the ventral roots and course to the dorsal horn. Most of these fibers were small in diameter and distributed boutons predominantly to the substantia gelatinosa. A few large ventral root afferent fibers were observed that distributed boutons mostly to the nucleus p

ISSN:0092-7317    

DOI:10.1002/cne.901790304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractTransneuronal degeneration in secondary brainstem auditory nuclei has been described following cochlear lesions, and Marchi studies have revealed degeneration in the trapezoid body after such lesions. These findings support the view of some early neuroanatomists that primary auditory afferents project beyond the cochlear nuclei. Silver impregnation studies of degenerating cochlear afferents have failed to support this claim, leaving the question unresolved. Using [3H] amino acides auditory projections in the monkey were traced autoradiographically from labeled ganglion cells: (1) in all portions of the spiral ganglion, (2) in apical and middle turns of the cochlea and (3) primarily in the basal turn of the cochlea.Labeling of the entire spiral ganglion resulted in profuse transport of isotope to parts of all cochlear nuclei [anteroventral (AVCN), posteroventral (PVCN), and dorsal (DCN) cochlear nuclei]. Labeled axons entering the trapezoid body (TB) projected ipsilaterally to: (1) the lateral trapezoid nuclei (LTN), (2) the lateral superior olivary nucleus (LSO), (3) the dorsal dendritic zone of the medial superior olivary nucleus (MSO), and (4) the pericollicular or cortical nucleus of the inferior colliculus (IC). Auditory fibers crossing the midline in the TB projected contralaterally to: (1) the medial trapezoid nucleus (MTN), (2) the ventral dendritic zone of the MSO, (3) the ventral nucleus of the lateral lemniscus (VNLL), and (4) the central nucleus of the inferior colliculus (CNIC). Selective labeling of cells in the apical and middle ganglionic turns of the cochlea resulted in a similar pattern of centripetal transport.Selective [3H] uptake primarily by ganglion cells in the basal turn of the cochlea resulted in: (1) labeling of restricted parts of all cochlear nuclei, and (2) a considerable reduction of isotope transported beyond the cochlear nuclei. Labeled fibers in the TB were distributed sparsely in the ipsilateral LTN, LSO and dorsal dendritic zone of the MSO. Fibers in the TB were not labeled contralaterally in these animals.Interpretation of these data considers the possibility of transneuronal isotope transport. The pattern of isotope transported beyond the cochlear nuclei does not correspond to the secondary projections of any individual cochlear nucleus, although it bears some resemblance to that of the AVCN. The current study suggests that some primary auditory afferents project beyond the cochlear nuclei.

ISSN:0092-7317    

DOI:10.1002/cne.901790305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractGanglion cell somata were drawn, measured and counted in flatmounted crucian carp and goldfish retinas stained with cresyl violet or methylene blue. Soma diameter histograms suggest that the ganglion cells can be divided into two populations with overlapping soma sizes: a large group of small cells and a small group of large cells, the latter constituting 2.5–5% of all ganglion cells. With increasing distance from the optic disc the mean soma diameter increases while the ganglion cell density decreases. In a peripheral growth zone close to the margin the ganglion cells become smaller again.The total number of ganglion cells in retinas of different size was calculated from the areas of the flat‐mounted preparations and the cell densities in two representative regions. In the crucian carp population used in this work the total number of ganglion cells per retina was found to increase from roughly 140,000 (mean of 8 scattered values) to a full 200,000 between eye diameters 4 and 10 mm, this increase taking place mainly between eye diameters of 4 and 6.5 mm.Thus, due to a drastically decreasing cell density, the total number of ganglion cells increases only by a factor of about 1.5 while the retinal area becomes sixfold. During the same growth period the mean soma diameter increases by a factor of about 1.3 and the soma volume more than doubles. The optic nerve of a small crucian carp was studied by electron microscopy. About equal numbers of unmyelinated and myelinated axons were found. The axons in the optic nerve are, on an average, considerably thicker than the axons on the retinal surf

ISSN:0092-7317    

DOI:10.1002/cne.901790306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractGanglion cells were studied in methylene blue stained flatmounted retinas. Three categories of cells are described: small (S) and large (L) ganglion cells in the main ganglion cell layer, and large ganglion cells (LD) with somata more or less displaced into the inner plexiform layer. These LD cells have two to four very thick primary dendrites and are identifiable as ganglion cells by their axons.An analysis of published data reveals that the large genglion cells of the crucian carp (types L and LD) have several striking characteristics in common with the large ganglion cells of the dogfish, the frog and the cat: (1) they are selectively stained by methylene blue; (2) they comprise only 2–5% of all the ganglion cells; (3) the large cells can be divided into two or three subtypes, and within each subtype the dendritic trees usually cover the retinal surface with a two‐ or threefold overlap.New ganglion cells are formed from neuroblasts at the retinal margin and most dendrites first grow along this neuroblastic zone. Thus the main dendrites of the L and LD cells tend to be oriented parallel to the margin all around the periphery of a crucian carp retina. Independent of the size of the eye this parallel orientation disappears at the same relative distance from the margin (about one‐third of the distance from the margin to the optic disc). If all L and LD cells are formed at the retinal margin and first develop oriented dendrites, we have to assume that the more randomly oriented dendritic trees in the central retina have undergone a reorganiz

ISSN:0092-7317    

DOI:10.1002/cne.901790307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractHistological and electrophysiological features of horizontal cells were studied in the stingray retina in which the ratio of rods to cones was about five to one. There were three distinct sublayers of horizontal cells; external, middle and internal. The type of horizontal cells recorded was identified by dye injection after recording. Relatively thick external horizontal cells sent their short dendrites into both rod and cone terminals to make synaptic contacts. The response recorded from them was not color‐coded but showed a Purkinje shift depending on the adaptational state. Middle horizontal cells were flat and usually two or three of them overlying each other constituted the middle sublayer. Their response, which was difficult to record in the light‐adapted retina, was characterized by a slow time course, a prolongation of the response to bright flashes and a maximum sensitivity in the green region of the spectrum without any sign of Purkinje shift. Internal horizontal cells were color‐coded. They responded with hyperpolarization at shorter wavelengths and with depolarization at longer wavelengths. It was concluded that the internal horizontal cells receive inputs from cones and the middle horizontal cells from rods, whereas the external horizontal cells receive inputs from both rods and

ISSN:0092-7317    

DOI:10.1002/cne.901790308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe laminar staining of the rat hippocampal region with the Timm sulphide silver method is from studies on adult rats known to depend on the various fibersystems terminating in these laminae. In order to illustrate the development of these fibersystems the laminar differentiation of the Timm staining of fascia dentata, hippocampus and subiculum is presented for rats between 1 and 31 days old. Corresponding changes in cytoarchitectonics as revealed by thionin staining are briefly demonstrated.Even on the first postnatal day there are indications of the mature, laminar staining pattern, and between three and nine days all the laminae corresponding to the terminal fields of the major afferent and intrinsic systems appear. After 12 days only minor additions to the laminar pattern develop, but there are adjustments of absolute and relative dimensions of layers and fields, and also the staining densities of individual laminae change.These observations are in good correlation with the available information on both hippocampal neurogenesis and cytodifferentiation, and the few fiber tracing studies performed on the developing hippocampal region. Compared to the latter, which ideally marks only one system or one lamina per animal, the Timm method provides an excellent means for getting an overview of the general developmental situation at the different ages. Thus developmental gradients along septo‐temporal, medio‐lateral and basal‐apical axes are found, which should be heeded in future studies on hippocampal synaptogenesis.The observations are discussed in relation to current models for neuronal growth and formation of nervous connec

ISSN:0092-7317    

DOI:10.1002/cne.901790309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractEmbryos were immobilized with neuromuscular blocking agents for one to four days between days 10 and 15 of incubation. This treatment reduces spontaneous motility, as well as movement‐initiated proprioceptive and cutaneous stimulation. Although the major aim of these experiments was to determine the effects of such treatment on subsequent behavioral development, several indices of neuromuscular and general morphological development were also examined.A single injection of curare on day 10 continues to depress spontaneous motility for virtually the entire remaining incubation period. This effect is due to the persistence of unmetabolized curare in the closed system of the egg. When a comparable dose of a rapidly metabolized neuromuscular blocking agent (succinylcholine) is given, this long term behavioral depression is not found. Embryos treated with SC can remain totally immobilized for up to 60 hours with no apparent repercussions on subsequent behavior; spontaneous embryonic motility, reflex sensitivity, hatching, and several general posthatching behaviors, all appeared normal following such treatment.Embryos immobilized for as little as 48 hours developed joint malformations and were retarded in general growth by about one day whereas 24 hours of paralysis was not sufficient to induce these effects.Twenty‐four hours of total paralysis from days 10 to 11, plus a 40–50% reduction in motility until days 15 or 16, does not appear to cause any abnormalities in muscle or spinal cord development. Muscle histology, motor endplates, cell number in the spinal cord and choline acetyltransferase and acetylcholinesterase activity in spinal cord and muscle were all comparable to controls. An 80–90% reduction in motility on days 11 through 15, however, induces an apparent alteration of the intensity and distribution of histochemically demonstrable AChE in the anterior and posterior latissimus dorsi muscles.The present findings suggest that the suppression of overt motility for a period comprising ca. 5–12% of the total incubation time (21 days) does not modify subsequent behavioral development or the underlying neurogenetic mechanisms. Though these findings provide some support for the notion that the embryonic nervous system develops inforward referenceto and without benefit from function or sensory input, only a more complete reduction of neural function, especially CNS activity, can provide a critical test of thi

ISSN:0092-7317    

DOI:10.1002/cne.901790310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe differential projections from the dorsal raphe and median raphe nuclei of the midbrain were autoradiographically traced in the rat brain after3H‐proline micro‐injections. Six ascending fiber tracts were identified, the dorsal raphe nucleus being the sole source of four tracts and sharing one with the median raphe nucleus. The tracts can be classified as those lying within the medial forebrain bundle (dorsal raphe forebrain tract and the median raphe forebrain tract) and those lying entirely outside (dorsal raphe arcuate tract, dorsal raphe periventricular tract, dorsal raphe cortical tract, and raphe medial tract). Thedorsal raphe forebrain tractlies in the ventrolateral aspect of the medial forebrain bundle (MFB) and projects mainly to lateral forebrain areas (e.g., basal ganglion, amygdala, and the pyriform cortex). Themedian raphe forebrain tractlies in the ventromedial aspect of the MFB and projects to medial forebrain areas (e.g., cingulate cortex, medial septum, and hippocampus). Thedorsal raphe cortical tractlies ventrolaterally to the medial longitudinal fasciculus and projects to the caudate‐putamen and the parieto‐temporal cortex. Thedorsal raphe periventricular tractlies immediately below the midbrain aqueduct and projects rostrally to the periventricular region of the thalamus and hypothalamus. Thedorsal raphe arcuate tractcurves laterally from the dorsal raphe nucleus to reach the ventrolateral edge of the midbrain and projects to ventrolateral geniculate body nuclei and the hypothalamic suprachiasmatic nuclei. Finally, theraphe medial tractreceives fibers from both the median and dorsal raphe nuclei and runs ventrally between the fasciculus retroflexus and projects to the interpeduncular nucleus and the midline mammillary body.Further studies were done to test whether the fiber tracts travelling in the MFB contained 5‐HT. Unilateral (left) injections of 5,7‐dihydroxytryptamine (5 μgm/400 nl) 18 days before midbrain raphe microinjections of3H‐proline produced a reduction in the grain concentrations in all the ascending fibers within the MFB. Furthermore, pharmacological and behavioural evidence was obtained to show that the 5‐HT system had been unilaterally damaged; these animals displayed preferential ipsilateral turning in a rotameter which was strongly reversed to contralateral turning after 5‐hydroxytryptophan administration.The results show that DR and MR nuclei have numerous ascending projections whose axons contain the transmitter 5‐HT. The results agree with the neuroanatomical distribution of the 5‐HT system previously determined biochemically, histochemically, and neurophysiologically. The midbrain serotonin system seems to be organized by a series of fiber pathways. The fast transport rate in these fibers was found

ISSN:0092-7317    

DOI:10.1002/cne.901790311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY